1. Field
The present invention relates to a feathering, flapping and rotor loads indicator for use in an aircraft rotor system.
2. Description of Related Art
Flight envelope limitations have been conventionally used to delineate the safe range of operation of an aircraft. Flight envelope limitations may be defined as the parameters within which an aircraft can be safely operated, with average pilot ability, at varying density altitudes, airframe states, wing or blade loadings and atmospheric turbulence. These limitations are determined based on flight test or laboratory data, which are used to calculate the stress, temperature or other measures of health of critical components during various flight conditions.
However, flight envelope limitations are typically very conservative. As a result, they generally reduce the overall operational capability of the aircraft. In addition, they are often difficult or impossible to consider during high workload operations such as combat maneuvering or terrain following.
To address this concern and to expand the allowable flight envelope of an aircraft, it has been proposed to use strain gages to provide pilots with information pertaining to the current condition of critical elements of the aircraft. For example, in rotorcrafts, it has been proposed to use strain gages to measure most-critical component loads. However, it is not common for a single component to be critical in all flight regimes. Additionally, strain gages are generally unreliable and their use increases the recurring cost of an aircraft because they require maintenance and dedicated instrumentation. Furthermore, strain gages are unable to provide information about the temperature of critical elastomeric bearings that are used, for example, in rotorcrafts.